-50.08% is the change from 643 to 321
Calculation steps:
[( 321 - 643 ) ÷ 643] x 100 = -50.08%
Formula
Percentage change = [(321 - 643) / 643] x 100
Subtract the new number by the original number
321 - 643 = -322
-322 ÷ 643 = -0.5007776049766719
-0.5007776049766719 x 100 = -50.08%